1. Field of the Invention
The present invention generally relates to a mobile communication system, and more particularly, to a method of managing a radio bearer of a mobile communication system.
2. Background of the Related Art
A general Packet Radio Service (GPRS) network is a wire network of a mobile service provider which provides a packet service. A related-art communication network and system for providing the packet service is shown in FIG. 1. This system includes a Gateway GPRS Support Node (GGSN) 15, a Serving GPRS Support Node (SGSN) 13, a Home Location Register (HLR) 14, a Universal Terrestrial Radio Access Network (UTRAN) 12 and a Mobile Station (NIS) 11.
The GGSN 15 functions as a gateway to be connected With Internet Protocol (IP) Network 16, and the SGSN 13 is connected to the GGSN 15 via the GPRS network for managing mobility of the MS 11 of a packet mode. The SGSN 13 also serves as a packet switch. The HLR 14 is connected to the GGSN 15 and the SGSN 13 for managing a subscriber's subscription information and a subscriber's location information. The UTRAN 12 manages a radio bearer and transmits data by allocating traffic channels.
A method for allocating and releasing a radio bearer in the aforementioned general packet mobile communication system will now be explained. In order to receive the GPRS of the packet service, a packet service subscriber registers his own location in the SGSN 13 via the MS 11. Upon registering the location of the subscriber via the MS 11, the SGSN 13 takes service information of the subscriber from the HLR 14. The SGSN 13 then performs the process for activating a Packet Data Protocol (PDP) context to set a Packet Session. That is, a radio source is assigned between the MS 11 and UTRAN 12 according to the desired quality of service. When setting the Packet Session by the process for activating the PDP context, the packet service is provided to the MS 11.
Next, if the subscriber desires to terminate the service, the SGSN 13 deactivates the PDP context by the process for deactivating the PDP context, and releases the assigned radio source. At this time, the GPRS packet service performs a PDP context Preservation function according to rarity of importance of the radio bearer. According to the PDP context Preservation function, the UTRAN 12 judges the necessity of releasing the radio bearer in case of User Inactivity or temporary cut-off of the radio bearer, and releases the radio bearer temporarily by an operation with the SGSN 13.
FIG. 2 is a signal flow chart illustrating the process of setting Radio Access Bearer (RAB) Release Request to release the radio bearer for the PDP context preservation function of the GPRS packet service. If the User Inactivity or the temporary cut-off of the radio bearer is detected, the UTRAN 12 sends the RAB Release Request message to the SGSN 13 (201). At this time, it is possible to request releasing the plurality of radio bearers simultaneously. The SGSN 13 receiving the RAB Release Request message sends a RAB Assignment Request message to the UTRAN 12 to release the radio bearer (S202). Therefore, a radio bearer is released between the UTRAN 12 and the MS 11 (S203), and the released radio bearer may be used in service for another subscriber. Then, the UTRAN 12 sends a RAB Assignment Response message to the SGSN 13 to respond the RAB Release Request message (S204). At this time, information for re-setting the radio bearer is maintained.
For receiving the packet service again following the PDP context preservation, the subscriber has to send a Service Request message to the SGSN 13 via the MS 11 to request the allocation of the radio bearer.
In the related art method of managing the radio bearer in the mobile communication system, the PDP context preservation function is performed according to the UTRAN 12 without determination of the subscriber. That is, the UTRAN 12 periodically checks the User Inactivity. When the User Inactivity generates for a predetermined time period, the radio bearer is released and the PDP context is preserved. Thus, until the UTRAN 12 checks the User Inactivity, the radio bearer cannot be used for another, which results in wasting the radio bearer.
The time period for maintaining the packet service is longer than that for maintaining a general circuit service of telephone communication network, so that the user may want to intentionally discontinue the service due to various reasons. For instance, the user may desire to discontinue the packet service due to the cut-off of the packet service by web server connection and e-mail, call or urgent business.
However, in the related art method of managing the radio bearer in the mobile communication system, the PDP context preservation function is performed according to the UTRAN 12 without determination of the subscriber. Therefore, the user has to deactivate the PDP context in order to terminate the service, which substantially decreases the efficiency of use of the radio bearer.